1. Field Of The Invention
The present invention relates to gas container valves. More particularly, it relates to an LP gas container valve capable of meeting disasters by preventing an abnormal outflow of gas due to a disaster from occurring when the container valve is fully opened in its state of normal use.
2. Description Of The Related Art
A property required of valves to be mounted on an inlet/outlet of a container for a high-pressure gas, such as an LP gas container, is the capability of satisfactorily carrying out such typical operations as the charging of gas, the recovery of residual gas and the gas blow test. In addition, as a countermeasure against such disasters as an earthquake or fire, other requirements include prevention of a secondary disaster resulting from the discharge of a large amount of gas due to a collapsed house or damage to the gas supplying facility and prevention of a gas discharge at the time a gas cylinder falls down so that an explosion of the cylinder does not occur even if the container is exposed to a flame in a fire. However, the technology completely satisfying these requirements has not yet been developed.
Of those described above, while a safety valve has been provided to prevent an explosion of the container due to an abnormally elevated pressure within the container, such a valve is incapable of preventing the discharge of a large amount of gas due to damage of the gas supplying facility.
As a countermeasure against the danger of fire, explosion, etc., there are safety valves which incorporate a cut-off valve to be actuated as a result of sensing an abnormal outflow of gas between the valve and the destination of the gas supply or a sensor mechanism for sensing an inclination of the gas container or the shaking of an earthquake and a gas cutting off section to be actuated by the sensor.
Generally, in the case where an LP gas cylinder or the like is provided at a consumer's house, a high-pressure collective automatic switching device is used and all of the individual container valves are fully opened. Accordingly, if a breakage occurs at some point in the gas supply due to an earthquake or an unexpected accident, it is very dangerous because a large amount of gas is discharged at the point of breakage. In such a case, the gas supply beyond the valve must be instantaneously shut down.
In a system using a separate cut-off device provided as an attached component part at the outlet of a conventional container valve, the mounting and fixing of the separate cut-off device to the surrounding structure is more complicated than the system in which only a conventional valve is used, even if the device itself is simple and securely operable. The level of safety is correspondingly lowered and the cost is higher.
Further, most of those systems incorporating an anti-earthquake gas cut-off mechanism into the gas container valve have not yet met all the objective conditions. For example, there is a system in which a tapered portion having a passage narrowed toward an outlet is provided in the gas passage between the gas container body and the closing/opening section of the valve and a movable ball is provided in the passage. When the gas flow rate is abnormally increased, the ball is abutted against the tapered portion to cut off the gas.
However, any such system using a gas cut-off ball is either without a safety valve or, even if a safety valve is present, is unstable and insecure in operation because the stationary position in normal operation of the ball is located in the gas passage on the side toward the gas container body from the branching point leading to the safety valve.
In particular, there is a danger of explosion with the system without a safety valve due to its inability to respond to an abnormally elevated gas pressure, for example, at the time of fire. Such a system lacks an indispensable element, a high-pressure gas container valve. In the system in which the normal stationary position of the ball is located toward the gas container body, the ball is drawn by suction toward the safety valve from the branching point when the safety valve is actuated, thereby closing the opening toward the safety valve and not allowing the normal operation of the safety valve. Even if the passage leading to the safety valve is widened compared to the conventional product in order to make it larger than the diameter of the ball, when the safety valve is actuated before the starting of an abnormal outflow of gas or when an abnormal gas outflow occurs in the state where the ball remains in a position toward the safety valve from the branching point as a result of the cylinder falling down with the safety valve facing down, it is impossible, only by the flow of the gas, to move the ball from that position toward the point for cutting off the abnormal outflow. There is thus a disadvantage with the system in that its purpose of cutting off the gas outflow cannot be achieved.